net: dsa: b53: Ensure the default VID is untagged

We need to ensure that the default VID is untagged otherwise the switch
will be sending tagged frames and the results can be problematic. This
is especially true with b53 switches that use VID 0 as their default
VLAN since VID 0 has a special meaning.

Fixes: fea8335 ("net: dsa: b53: Fix default VLAN ID")
Fixes: 061f6a5 ("net: dsa: Add ndo_vlan_rx_{add, kill}_vid implementation")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_common.c

@@ -1366,6 +1366,9 @@ void b53_vlan_add(struct dsa_switch *ds, int port,
 
 		b53_get_vlan_entry(dev, vid, vl);
 
+		if (vid == 0 && vid == b53_default_pvid(dev))
+			untagged = true;
+
 		vl->members |= BIT(port);
 		if (untagged && !dsa_is_cpu_port(ds, port))
 			vl->untag |= BIT(port);